Map 3096 U.S
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Scientific Investigations Map 3096 U.S. Department of the Interior Prepared for the Atlas Of Mars: MTM –40277, –45277, –40272, and –45272 Quadrangles U.S. Geological Survey National Aeronautics and Space Administration Pamphlet accompanies map 89° 90° 88° 90° 87° 270° 86° 272° 271° 270° 85° 273° 80° 274° –37.5° 84° 275° SEQUENCE OF MAP UNITS AND VOLATILE ACTIVITY 280° Hellas 83° 276° –37.5° Hc1 82° 277° HNps RIM ASSEMBLAGE FLOOR ASSEMBLAGE VALLIS AND CHANNEL MATERIAL CRATER MATERIAL VOLATILE ACTIVITY 81° 278° PERIOD 279° –38° 80° Nph cu cf 280° AHc2 AHc2 rim HNps –37.5° Hellas Hc1 –38° Gullies and Hellas ice-rich flows cu Nph highlands –38° AHc2 HNps Figure 4B cu Hc 1 Hella s rim Nph AMAZONIAN AHc3 Hellas Hc1 AHfs –38° AHvD ellas Nph HNps AHpc AHvt AHvD AHvH AHvS H AHc2 Dao, Harmakhis, HNps fl r s oo i –39° and Sungari Valles floor Nph l l AHc a 2 cf V Figure 4A HNfis basin o a A HNps D Nph –39° –47.5° Hfh Hc1 ABFigure 5. A comprehensive search of all MOC narrow-angle images within a 20° –39° Nph HNps cf cu by 20° area (A; lat 30°–50° S., long 270°–290° W.) of the eastern rim reveals AHc2 Fluvial channels HNps HESPERIAN –8,200 m Globe 4,000 m layered deposits at each of the locations identified by a yellow dot. Parts of MOC Nph Hc 1 HNps narrow-angle images E2000151 (B; image center, lat 41.27° S., long 275.71° W.) cu C Hc1 and E2200427 ( ; image center, lat 41.09° S., long 275.21° W.) show intricate –39° AHv HNps HNfis AHc2 D HNps –7,000 m Inset –4,000 m curvilinear patterns found in finely layered deposits concentrated in the AHv Nph Nph D A hummocky plains material ( ) of the rim assemblage (image widths ~3 km). cf Figure 1. ( ) Hellas Planitia extends across ~50° in longitude (long ~46° to 95° E.) and more than 20° in BC Nph Red line, –5,000 m contour. –40° latitude (lat ~32° to 55° S.). The –4,000 m elevation contour roughly defines the topographic depression of Mliba B AHc3 Nph the Hellas basin. ( ) MTM –40277, –45277, –45272, and –40272 quadrangles traverse the eastern rim of cu Hellas Planitia and display ~3 km of relief, including the transition from rim to floor. Mars Orbiter Laser cf AHvS cp Altimeter (MOLA) DEMs (128 px/degree, ~464 m/pxl). Note locations of informally named features Nph Hellas Planitia cu discussed in report. cf Paleo-lakes? cu HNps –40° Nph AHvt –40° AHc3 Nph Nph NOACHIAN 45° 105° Nph 315° 255° cf –20° Nph –1,800 m –40° AHvS HNps –3,100 m Figure 6 HNps cu AHc AHc s –5,800 m 2 3 l l i –41° Va Channel floor material (Amazonian to Hesperian) Hc1 cf DESCRIPTION OF MAP UNITS –6,900 m r i a AHc3 Member 3 (Amazonian to Hesperian)—Smooth surfaces in elongate, Hc g AHv 1 u n RIM ASSEMBLAGE D HNps S sinuous channels; low albedo. Occurs on floors of youngest through- AHpc Nph cu Tungla Channeled plains material (Amazonian to Hesperian)—Smooth to cutting canyons and channels superposing the vallis terminal material 5,000 m –41° Type Locality HNfis irregular surfaces characterized by small-scale sinuous channels, at the mouth of Dao Vallis. : lat 39.6° S., long 277.8° W. cf Santaca ridges, and scarps; lightly cratered. Type Locality: (lat 45.5° S., long Interpretation: Fluvial, aeolian, and (or) mass-wasted materials depos- –41° AHv S 271.3° W.). Interpretation: Sediments deposited as result of erosion of ited in narrow topographic lows surrounding highlands to the east and of Hellas Planitia rim terrain; AHc2 Member 2 (Amazonian to Hesperian)—Smooth surfaces in truncated Hc AHvH redistributed to form smooth and scoured (to the east) surfaces. channel segment. Channels typically have narrow, sinuous form, but cu HELLAS 1 Nph HNps HNfis Type Locality –4,000 m i s Uncertainty regarding exact location of contact with unit results also show widening in some locations as open canyons. : l l Interpretation –41° HNfis a from presence of poorly consolidated sediments and Amazonian lat 39.05° S., long 275° W. : Channel floor containing Nph HNps cu HNps V cu mid-latitude mantling deposits. Some contributions of sediments and deposits of fluvial, aeolian, and (or) mass-wasted material; widening –8,200 m Nph caused by wall collapse. Channel segments reflect drainage along s volatiles may be related to development of Reull Vallis to the east of the –60° h i cu a k –42° map area or Hellas Planitia paleolakes Hellas Planitia rim; some may represent abandoned pathways of Dao Figure 2. MOLA 128 pixel/degree DEM with contour intervals or shorelines: a r m H HNps Smooth plains material (Hesperian to Noachian)—Plains of slight to Vallis paleochannels –6,900 m, –5,800 m, and –3,100 m (Moore and Wilhelms, 2001, 2007) and –1,800 Hc1 cu cf cu moderate relief cut by narrow, sinuous channels and linear to arcuate Member 1 (Hesperian)—Smooth surfaces in truncated channel m (Crown and others, 2005). Shorelines follow and are characterized by distinct –6,400 m segments. Occurs along trend of several small surface channels. Chan- troughs. Forms low-relief plateau with a moderate albedo in Viking and changes in surface morphology, including crater retention. Figure 6. MOLA DEM (left) and Viking MDIM 2.1 (right) showing several truncations along Dao Vallis on nels typically have narrow, sinuous form but also show widening in Nph Quines THEMIS visible datasets; exhibits ridges and curvilinear to irregular the eastern rim of Hellas basin. Image locations shown on map. See map symbol explanation at end of –42° some locations as open canyons. Type Locality: lat 39.3° S., long 274° Figure 7 Hc1 scarps, many along the margins of Dao Vallis. Stipple pattern marks Description of Map Units. W. Interpretation: Channel floor containing deposits of fluvial, aeolian, –42° regions of downdropped blocks of smooth plains material that preserve primary surface characteristics. Type Locality: lat 41° S., long 273.8° and (or) mass-wasted material; widening caused by wall collapse. Hfh W.; blocks at lat 38.8° S., long 272.8° W. Interpretation: Sedimentary Channel segments reflect drainage along Hellas Planitia rim; some may deposits derived from surrounding terrains and possible volcanic mate- represent abandoned pathways of paleochannels AHv rial; large irregular blocks represent initial stages of canyon widening D Dao Vallis floor material (Amazonian to Hesperian)—Smooth materials MN No. of craters with >16 km diameter per 10 –42° due to fracturing, sapping, collapse, and possible devolatilization on floor of elongate, relatively steep walled, sinuous canyon; linear and AHvH Type Locality Hfh Nph Hummocky plains material (Noachian)—Irregular surfaces of moderate curvilinear features parallel canyon margins. : lat 39.4° S., long 273.55° W. Interpretation: Materials derived from surrounding 2 400 100 HNfis relief; moderately to heavily cratered and cut by numerous channels HNfis –43° km Nph and scarps; mottled appearance with high-standing knobs, ridges, units, canyon walls, and (or) aeolian deposition; modified by small- 6 Hfh scale deflation and redistribution. Lineations may be related to flow of cf cu troughs, and layered outcrops along scarps; low albedo relative to HNps water/ice-rich materials downcanyon or due to convergence of debris AHfs smooth plains material (unit ) in Viking and THEMIS visible AHfs shed from adjacent walls AHv images; highly variable thermophysical signature in THEMIS infrared 300 LN 75 H AHv cu cu –43° images. Diamonds indicate layered materials observed in high- H Harmakhis Vallis floor material (Amazonian to Hesperian)—Smooth AHfs resolution MOC images, see figure 5. Type Locality: lat 38.1° S., long materials on floor of elongate, relatively steep walled, sinuous canyon; –43° Nph 275.3° W. Interpretation: Sedimentary and volcanic deposits with surface lineations and chains of pits parallel canyon margins. Type HNfis HNfis HNfis HNps HNfis some remnants of rugged highlands. Irregular surface morphology, Locality: lat 41.9° S., long 271.6° W. Interpretation: Materials derived albedo, and thermophysical mottling result from deformation, defla- from surrounding units, canyon walls, and (or) aeolian deposition, 200 25 6 Hfh Nph tion, fluvial downcutting, scarp retreat, and collapse of layered, possi- modified by small-scale deflation and redistribution; lineations either EH km bly water/ice-rich, materials. Heavily cratered inselberg on floor of from flow of water/ice-rich materials downcanyon or from 2 HNfis Nph –43° Hellas Planitia (lat 46° S., long 275.5° W.) represents lateral continua- convergence of debris shed from adjacent walls; pits from loss of HNfis tion of rim assemblage underneath smooth floor deposits (unit ); volatiles or from collapse of surface materials over subsurface volatile No. of craters with >5 km diameter per 10 100 cu pathways LH –44° Hellas basin floor exposure displays both old, degraded crater rims, as HNfis Nph well as superposed fresh craters, indicating some removal of a cover AHvS Sungari Vallis floor material (Amazonian to Hesperian)—Smooth mate- material, possibly unit AHpc. Current surface morphology appears to rials on floor and at terminus of narrow, elongate, sinuous canyon. Type EA AHfs cu HNfis be dominated by aeolian deflation, devolatilization, and collapse Locality Interpretation Hfh : lat 40.25° S., long 272.15° W. : Canyon floor 0 containing deposits of fluvial, aeolian, and (or) mass-wasted material AHpc Hfh HNps HNfis Nph –44° FLOOR ASSEMBLAGE Figure 3. Graphical representation of N(5) (black) and N(16) (red) size Hfh AHfs Smooth fill material (Amazonian to Hesperian)—Smooth, relatively CRATER MATERIAL –44° frequency distributions for major geologic units. N(16) scale is featureless surface in Viking and THEMIS visible images, confined to cf Crater-fill material (Amazonian to Noachian)—Smooth, relatively nonlinear, but age divisions (Tanaka, 1986) correlate with N(5) topographic depressions marking the extensions of Harmahkis Vallis featureless surfaces on crater floors.